In various nuclear processes such as nuclear power generation utilizing boiling water reactors (BWR), the possibility of environmental radiation hazards are continually presented. For example, where the turbine leakage air, etc. that enters the steam condenser of a typical system is subsequently vented therefrom as "off-gas" to atmosphere, radiation hazards clearly exist. That is, air in leakage into the condenser and turbine will sweep with it radioactive krypton and xenon fission products that are released by leakage from reactor fuel elements. The contaminated leakage air constituting the off-gas cannot therefore be safely vented to atmosphere. In another application, such as nuclear-fuel reprocessing plants, fuel elements are processed and dissolved for recycling and fission products including radioactive krypton and xenon which are of primary concern here, are released to constitute together with air or other carrier such as nitrogen or argon generated by other nuclear processes, the off-gas stream. In both instances, the radioactive fission products described above cannot be vented directly to atmosphere because of radiation hazard and therefore must be isolated or stored for a required period so as to be rendered harmless.
A number of different systems for removing radioactive contaminants from reactor and other nuclear process off-gases have been proposed; in general, these systems require continuous monitoring by station personnel, are complicated and expensive, and in some instances impractical for long range operation. For example, systems using adsorbers, solvent baths, etc. have been proposed for capturing and separating the radioactive gases from the off-gas stream. None of these systems has efficiently and economically achieved rapid separation, concentration and compact system storage of the radioactive krypton and xenon in the off-gas streams; nor are the prior art systems capable of maintaining completely safe isolation of the longer lived radioactive krypton from the environment.
The present invention is concerned with providing an improved and simplified system for safely isolating radioactive noble gases from the environment and is applicable to systems for removing krypton and xenon from air, argon, nitrogen, CH.sub.4, CO and mixtures thereof as applied to nuclear power plants of the boiling water reactor, pressurized water reactor, fast flux and breeder reactor types or any other reactors that generate the above gas mixtures. In addition, the present invention is applicable to the treatment of off-gases such as the foregoing mixtures developed by nuclear fuel processing, reprocessing and manufacturing operations,